I have main unit.
type Nintendo Game Boy attachment
The Konami Hyperboy — Game Boy Enhancement Device
The Konami Hyperboy was a peripheral accessory for the Nintendo Game Boy — a device that the Game Boy slotted into, providing a larger display through magnification, external speakers for improved sound, and a joystick controller for more comfortable gameplay. Konami produced this enhancement device recognising that the original Game Boy’s small screen and quiet built-in speaker limited the gaming experience, and that players might welcome a more console-like setup for home use while retaining the Game Boy’s portability for travel. The Hyperboy represents the accessory ecosystem that grew around Nintendo’s dominant handheld platform throughout the early 1990s.